It is not easy to accurately and reliably vacuum-chuck a light, minute workplace having a size on the order of several hundreds of micrometers to several millimeters, to reliably release the vacuum-chucked workplace, and to accurately and reliably place the released workpiece on a workplace placement surface, for the following reasons. For a light, minute workpiece having a size on such an order, the influence of the gravity as well as an electrostatic force and interface energy cannot be ignored. For an ordinary method of merely applying and releasing a holding force or a vacuum-chucking force, it is not easy to place such a workplace on or remove the workpiece from a placement surface. Also, it is not easy to manufacture a vacuum chuck member in accordance with dimensions of such a workpiece and to accurately set the vacuum chuck member in accordance with the position and posture of the workpiece.
Conventionally employed devices for vacuum-chucking such a light, minute workpiece and releasing and placing the workpiece on, a placement surface include a workpiece vacuum chuck head and a workpiece vacuum chuck device disclosed in Japanese Patent Application Laid-Open (kokai) Nos. H5-235594 and 2003-165083, respectively.
The former device has a pusher provided within a negative-pressure chamber of the vacuum chuck head in order to reliably release an electronic component. Upon release of a negative pressure in the negative-pressure chamber, a pushing bottom end portion of the pusher projects from a suction hole so as to push a workpiece vacuum-chucked on a vacuum chuck surface, thereby helping the workpiece to be released from the vacuum chuck surface. However, this device does not have a follower mechanism for causing the vacuum chuck surface to follow the workpiece placement surface.
The latter device has a coil spring (first buffer mechanism) disposed between a vacuum chuck nozzle body and a holder section, in which the vacuum chuck nozzle is accommodated, and a thin-walled portion (second buffer mechanism) provided inside the vacuum chuck nozzle body in order to reduce an impact load associated with pushing of the vacuum chuck nozzle against a thin, minute workpiece, such as an electronic component, for vacuum-chucking the workpiece, and an impact load associated with attachment of the vacuum-chucked workpiece onto a substrate, thereby preventing cracking or chipping-off of the workpiece. The thin-walled portion (second buffer mechanism) is a particularly thin-walled structure formed between a nozzle tip, which is located at the front end of the vacuum chuck nozzle body, and a nozzle intermediate-portion, which is located at the root of the vacuum chuck nozzle body. When the nozzle chip is pushed against a workpiece for vacuum-chucking the workpiece and for attaching the vacuum-chucked workpiece to a substrate, first, the thin-walled portion (second buffer mechanism) is deformed; then, the coil spring (first buffer mechanism) is compressed according to the magnitude of the pushing force. This can mitigate or prevent the above-mentioned occurrence of an impact load and cracking or chipping-off of the workpiece.
However, the latter device does not have means for reliably releasing a vacuum-chucked workpiece from the nozzle tip. Also, although the thin-walled portion (second buffer mechanism) can be deformed along the axial direction of the nozzle tip in order to reduce an impact load associated with pushing of the vacuum chuck nozzle against the workpiece and to prevent cracking or chipping-off of the workpiece, a workplace chuck surface formed on the end face of the nozzle tip is small in area, implying that at a design stage the workplace chuck surface is not expected to exhibit a function of following an inclination of a workplace placement surface.
Japanese Utility Model Publication (kokoku) No. S50-14070 discloses a workpiece vacuum chuck device having the following function for causing a workpiece vacuum chuck surface to follow an inclination of a workplace placement surface. However, this device is not intended to vacuum-chuck and attach a light, minute workpiece having a size on the order of several hundreds of micrometers to several millimeters and thus is not devised to handle such workplaces.    Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. H5-235594    Patent Document 2: Japanese Patent Application Laid-Open (kokai) No. 2003-165083    Patent Document 3: Japanese Utility Model Publication (kokoku) No. S50-14070